System and Method for Determining Volume of Fluid in a Tank

ABSTRACT

Volume of a fluid, such as gasoline or diesel fuel, in a tank is determined by measuring the pressure of the fluid using a pressure sensor positioned proximate the bottom of the tank. The depth of the fluid in the tank is then calculated by dividing the pressure by the density of the fluid. Fluid volume is then determined mathematically or from charts given the depth as well as the size and shape of the tank. Multiple pressure readings may be taken along or near the bottom of a tank, and an average pressure determined that may be used to calculate measured volume. To maintain accuracy at different altitudes, pressure readings are preferably adjusted for atmospheric pressure using differential pressure sensors or a processor using data indicative of both pressures. Volume changes exceeding a predetermined threshold, or which are not comparable to dispensed fuel, may be flagged and alerts generated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.14/529,118 filed Oct. 30, 2014, which claimed the benefit of U.S.Provisional Application No. 61/897,426, filed Oct. 30, 2013, and thisapplication is a continuation-in-part of U.S. application Ser. No.15/391,813, filed on Dec. 27, 2016, which is a continuation-in-part ofU.S. Pat. No. 9,528,872, formerly U.S. application Ser. No. 14/529,137,filed on Oct. 30, 2014, and issued on Dec. 27, 2016, which claimed thebenefit of U.S. Provisional Application No. 61/897,426, filed on Oct.30, 2013, all of which applications are hereby incorporated herein byreference, in their entirety.

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to systems and methods fordetermining at least one of the volume and quality of fluid in a tankand, more particularly, to systems and methods for determining thevolume and quality of a fluid, such as gasoline or diesel fuel, used,for example, in a commercial transportation vehicle fleet.

BACKGROUND OF THE INVENTION

Vehicles, such as automobiles and trucks, require fuel to operate, suchfuel as electric power, propane, hydrogen, gasoline, diesel fuel,liquefied natural gas (LNG), liquefied petroleum gas (LPG), and thelike. Fuel must be stored in a fuel container such as, by way ofexample, one or more fuel tanks or batteries, and it can be appreciatedthat it is important that fuel not leak from a tank or be used morequickly than anticipated by a fuel system (e.g., leaking fuel supplylines or inappropriate operating engine conditions resulting inexcessive fuel usage). This is even more important in the case ofcommercial tractor trailers that often must travel long stretches ofhighway between service stations. Further, if fuel leaks from a fueltank, it could be dangerous as it could ignite into a fire or evenexplode, with obvious implications of danger to surroundings, includingpeople in the vicinity.

Fuel losses may occur in other ways as well, such as by theft. Forexample, it is not uncommon for commercial vehicle operators to usecompany charge cards for purchasing fuel in large quantities.Unscrupulous vehicle operators have been known to make fuel charges forfuel which was not added to the fuel tank of the approved vehicle, butinstead added to the fuel tank of an accomplice vehicle operator'svehicle for which the accomplice may give the unscrupulous vehicle ownera monetary kickback. Other schemes derived by unscrupulous vehicleoperators include collusion with service station operators to overchargecompany charge cards in exchange for a monetary kickback and siphoningfuel from the fuel tank. Service stations, truck stops or other fueldispensing entities have even been known to heat diesel fuel to increasethe volume as registered by the dispensing unit whereby the customer'senergy value (i.e., BTU's) per gallon of received or dispensed fuel isdecreased. Fuel dispensing entities have also been known to adjust fueldispensing units to show more fuel delivered than is actually dispensedeven though the fuel has not been heated.

To identify and confirm a fuel loss from a vehicle, whether the fuelloss be the result of leakage, inappropriate engine operatingconditions, or theft, fuel volume must be accurately and reliablymeasured. There are a number of fuel volume measurement sensorsavailable for doing that, including a mechanical or magnetic floatsensor, an air bubbler sensor, a capacitive or radio frequency (“RF”)sensor, a differential pressure (DP) level sensor, an electricalconductivity or resistance sensor, an optical sensor, a pressuremembrane sensor, a radar or microwave sensor, and sonic or ultrasonicmeters. The cited fluid volume measurements are described in greaterdetail at, for example,http://www.globalspec.com/learnmore/sensors_transducers_detectors/level_sensing/level_sensing_devices_all_types,but suffice here to say that all are either inaccurate, unreliable, notsuitable for fuel, difficult to retrofit, and/or prohibitively expensiveto implement.

In light of the foregoing, an ongoing need exists for systems andmethods that can identify and confirm a fuel loss from a vehicle,whether the fuel loss be the result of leakage, inappropriate engineoperating conditions, or theft, so that appropriate measures may betaken to prevent same from continuing and/or occurring in the future.Still further, it would be desirable that such systems and methods wouldoptimize the fuel consumption cycle, including purchase, verification,and performance, for not only a single vehicle, but for a fleet ofvehicles. In the implementation of such systems and methods, it would bedesirable to have a fuel volume sensor that is accurate, reliable,suitable for fuel volume measurements, easy to retrofit, and notprohibitively expensive.

SUMMARY OF THE INVENTION

The present invention accordingly provides a system and method fordetermining volume of a fluid in a tank by first measuring the pressureof fluid proximate to the bottom of the tank. The depth of the fluid isthen determined from the pressure and density of the fluid. Fluid volumeis then determined mathematically or from charts given the depth as wellas the size and shape of a tank. Multiple pressure readings may be takenalong the bottom of a tank, and an average pressure determined that maybe used to calculate volume. Pressure readings may be taken at differentheights to determine fluid density used to calculate volume. Pressurereadings may be adjusted for atmospheric pressure. Volume increases ordecreases exceeding a predetermined threshold may be flagged and alertsgenerated. Volume calculations may be recorded for comparing against avolume of fluid recorded as being purchased.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand the specific embodiment disclosed may be readily utilized as a basisfor modifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures in which correspondingnumerals in the different figures refer to corresponding parts and inwhich:

FIG. 1 is a schematic block diagram exemplifying one embodiment of asystem for continuously determining volume of a consumable in anyvehicle in a commercial vehicle fleet, according to the teachingspresented herein;

FIG. 2 is a schematic block diagram exemplifying a remote serverdepicted in FIG. 1;

FIG. 3 exemplifies a tractor depicted in FIG. 1;

FIG. 4 is a schematic block diagram exemplifying an onboard computersubassembly utilized on the tractor of FIG. 3;

FIG. 5A is a flowchart exemplifying steps in a process for determiningat a remote server whether a fuel event has occurred, according toteachings presented herein;

FIG. 5B is a flowchart exemplifying steps in a process for determiningat a vehicle whether a fuel event has occurred, according to teachingspresented herein;

FIG. 6 is a graphical block diagram depicting one embodiment ofoperational modules, which form a portion of the system for determiningvolume of a consumable exemplified in FIG. 1;

FIG. 7 is a screenshot exemplifying details of a Dashboard reportdepicted by FIG. 6;

FIG. 8 is a screenshot diagram exemplifying details of an event depictedin the screenshot of FIG. 7;

FIG. 9 is a screenshot exemplifying details of a User AccessConfiguration form depicted in FIG. 6;

FIG. 10 is a screenshot exemplifying details of a Fuel PurchaseReconciliation Report depicted in FIG. 6;

FIG. 11 is a screenshot exemplifying details of a Vehicle Fuel reportdepicted in FIG. 6;

FIG. 12 is a screenshot exemplifying details of a Fuel Loss Eventsreport depicted in FIG. 6;

FIG. 13 is a screenshot exemplifying details of a Daily Fuel Logs reportdepicted in FIG. 6;

FIG. 14 is a screenshot exemplifying details of a Fuel Purchase Logsreport depicted in FIG. 6;

FIGS. 15A and 15B is a screenshot exemplifying details of a Fuel ProbeConfiguration form depicted in FIG. 6;

FIGS. 16A and 16B is a screenshot exemplifying details of a FuelPurchase Report Configuration form depicted in FIG. 6;

FIGS. 17A and 17B is a screenshot exemplifying details of a ReportConfiguration form depicted in FIG. 6;

FIGS. 18A and 18B is a screenshot exemplifying details of an AlertsConfiguration form depicted in FIG. 6;

FIG. 19 is a screenshot exemplifying details of a product configurationform depicted in FIG. 6;

FIG. 20 is a screenshot exemplifying details of a Firmware Updates formdepicted in FIG. 6;

FIG. 21 is a graphical schematic diagram exemplifying one embodiment offuel optimization application of the system for determining volume of aconsumable;

FIG. 22 exemplifies a single fuel volume sensor configured for insertioninto a fuel tank of the tractor of FIG. 3;

FIG. 23 is a schematic block diagram of the fuel volume sensor of FIG.22;

FIG. 24 is a cross-section of a tube taken along line 24-24 of FIG. 22;

FIG. 25 exemplifies a dual fuel volume sensor configured for insertioninto a fuel tank of the tractor of FIG. 3;

FIG. 26 illustrates the dual fuel volume sensor of FIG. 25 inserted in afuel tank of the tractor of FIG. 3; and

FIGS. 27 and 28 exemplify a mechanism that may optionally be employed tostabilize the dual fuel volume sensor of FIG. 25.

DETAILED DESCRIPTION OF THE INVENTION

Refer now to the drawings wherein depicted elements are, for the sake ofclarity, not necessarily shown to scale and wherein like or similarelements are designated by the same reference numeral through theseveral views. In the interest of conciseness, well-known elements maybe illustrated in schematic or block diagram form in order not toobscure the present invention in unnecessary detail, and detailsconcerning various other components known to the art, such as computers,workstations, data processors, databases, pressure and temperaturesensors, data communication networks, radio communications, electricalpower sources such as batteries and the like necessary for the operationof many electrical devices and systems, have not been shown or discussedin detail inasmuch as such details are not considered necessary toobtain a complete understanding of the present invention, and areconsidered to be within the skills of persons of ordinary skill in therelevant art. Additionally, as used herein, the term “substantially” isto be construed as a term of approximation.

It is noted that, unless indicated otherwise, computational andcommunication functions described herein may be performed by a processorsuch as a microprocessor, a controller, a microcontroller, anapplication-specific integrated circuit (ASIC), an electronic dataprocessor, a computer, or the like, in accordance with code, such asprogram code, software, integrated circuits, and/or the like that arecoded to perform such functions. Furthermore, it is considered that thedesign, development, and implementation details of all such code wouldbe apparent to a person having ordinary skill in the art based upon areview of the present description of the invention.

For definitional purposes, the following terms will be used herein andthroughout this disclosure. The term “fuel” includes any form ofconsumable energy, such as, by way of example but not limitation,electric power and fluids, both liquid and gaseous, such as gasoline,diesel fuel, propane, liquefied natural gas (LNG), liquefied petroleumgas (LPG), hydrogen, and the like, received from a fuel station. Theterm “fuel station” or “fueling station” includes any source ordispenser of fuel.

The term “volume” shall be used interchangeably and synonymously withthe term “quantity” to refer to a volume or quantity of a liquid, or ofa gas under a specified pressure, or the quantity of amperes-hoursavailable at a given voltage from a source of electrical power, such asa battery. More specifically, when referring to the detected volume offuel in a container or tank of a vehicle, it may be referred to as“measured volume”. When referring to the volume of fuel dispensed by apump at a fuel dispensing entity (e.g., at a the POS (point of sale)entity) or otherwise inserted in a tank as shown by the POS data, it maybe referred to as “dispensed volume”.

The term “quality” will used herein with reference to fluid fuels torefer to the energy, such as may be measured using British Thermal Units(BTU's), available per volumetric unit of a liquid or of a gas under aspecified pressure.

Referring now to FIGS. 1 and 2, there is depicted a system for keepingtrack of at least detected or measured volume and also in someembodiments the calculated quantity and/or quality of a consumableenergy source, which system is schematically illustrated and designatedby the reference numeral 10. The system 10 includes a remote server(“RS”) 16. As shown in FIG. 2, RS 16 includes at least a processor 202and memory 204 interconnected via a bus 210. Memory 204 is effective forstoring a database and computer program code executable by processor 202for performing functions in accordance with principles of the invention,preferably as a communication web-implemented application, discussed infurther detail below. RS 16 further includes capacity for a number ofinputs and outputs (“I/O”) 206, also discussed below.

Returning to FIG. 1, the system 10 further preferably includes at leastone fuel dispensing station (“FDS”) (sometimes also referred to as apoint of sale or “POS”) 20. FDS 20 is configured for supplying ordispensing a consumable energy source, referred to herein as “fuel”, toat least one vehicle, such as a tractor 24 pulling a trailer 26, or anyof a number of other types of vehicles, such as trucks (e.g.,large-transport-on-highway vehicles), automobiles, trains, boats, ships,airplanes, railroad locomotives, electric transport vehicles,construction vehicles, municipality fleets, vehicle-independentapplications (e.g., oil & gas drilling rigs), and the like, referred tocollectively herein as a “tractor”. By way of example, but notlimitation, the term “fuel” as used in this application, including theclaims, includes any consumable energy source such as gasoline, diesel,propane, hydrogen, electrical energy, oil, alcohol, urea, or other fuelor fluid, and the like, and combinations thereof (e.g., gasoline andalcohol). Thus the fuel may be stored in many types of fuel storagetanks or containers, also referred to herein as “fuel tanks”, or simply“tanks”, and including batteries. FDS 20 is preferably further adaptedfor receiving payment of fuel by way of a charge card, such as fuelcards, credit cards, and debit cards, in exchange for providing fuel,and for generating from such sale, fuel dispensed data 30. Fueldispensed data 30 preferably includes an invoice number, anidentification of who and/or for which vehicle fuel was purchased, alocation, date, and time of a purchase, a quantity (e.g., number ofgallons) and cost of fuel purchased, the cost including total cost aswell as price per unit (e.g., gallon) of fuel purchased. Mileage oftractor 24 is optionally provided as well with the fuel dispensed data.Fuel dispensed data 30 preferably excludes any proprietary information,such as the number of a charge card that could be used to commit fraudagainst the legitimate holder of the card. FDS 20 is coupled via anetwork 28 for transmitting fuel dispensed data 30 to RS 16. Network 28may comprise both wireless portions (e.g., cellular, satellite, Internetcompatible signal transmission towers, Wi-Fi, and other similar networkfacilities) and/or wired portions effective for data communication. Asindicated in FIG. 1, for typical FDS units located on a highway, thisdata would be transmitted via a data communication network 28, andoptionally through an intermediate server (“IS”) 18 utilized by aclearinghouse, financial institution, or the like that is set up tohandle charge card transactions for the FDS. As shown, the IS server 18is coupled via network 28 for forwarding fuel dispensed data 30 to RS 16via I/O 206.

As is readily apparent, a trucking company may well have ownership orsome controlling interest in one or more locations providing a refuelingentity that may be used to provide POS-type data and this refuelingentity may have associated fuel dispensed data of the type mentionedabove in connection with FDS 20 transmitted directly from the refuelingentity to RS 16 via data communication network 28 thus eliminating anyneed for an IS 18. Thus, IS 18 is shown in dashed line format sinceclearinghouse type action would not always be required.

As discussed in further detail below with respect to FIG. 3, tractor 24preferably includes a fuel sensor 104 positioned in each of at least onefuel tank, and is effective for measuring characteristics of fuel,referred to herein as fuel log data 32, discussed in further detailbelow with respect to FIG. 4, and for transmitting that fuel log data toan onboard computer assembly (“OCA”) 102, mounted on the tractor. OCA102 is coupled via network 28 for transmitting fuel log data 32 to RS 16via I/O 206. As discussed in further detail below with respect to FIG.23, a “mesh buffer” may optionally be positioned in or over the inputport of fuel sensor 104 to dampen fluctuations in fuel pressure whichmay result from vibration, vehicle acceleration and de-acceleration, andany accompanying sloshing of fuel in a fuel tank.

At least one work station 12 is also coupled to RS 16 via network 28.Work station 12 preferably includes a processor and memory (not shown)configured for storing computer program code executable by the processorfor providing an interface between RS 16 and a user. While not shown, a“user”, as the term is used herein, includes, by way of example but notlimitation, a transportation fleet administrator or manager, or atransportation carrier or logistics provider responsible for managing afleet of tractors, such as tractor 24, to haul various goods ontrailers. Work station 12 preferably also includes conventional computerinput devices, such as a keyboard and mouse, and output devices, such asa display monitor 13.

FIG. 3 depicts in greater detail a tractor 24 equipped for functioningin accordance with principles of the invention. The tractor 24 includesan engine compartment 40 housing an engine and other components, as wellas a cabin 48 positioned behind engine compartment 40 and above avehicle chassis 50. Two storage tanks, referred to herein as fuel tanks,64 (only one of which is shown) are typically mounted to the vehiclechassis 50 anterior to cabin 48. As is well known, a majority oflate-model trucks throughout the world include a Controller Area Network(“CAN”) comprising a computer network or bus formulated by the vehicle'selectronic control units for transmitting or relaying messages betweensensors, electronic control circuits and controlled devices throughoutthe vehicle. Thus, a block 103 representing the CAN system is shown asbeing part of the vehicle 24.

In one embodiment, the system 10 components associated with tractor 24include, but are not limited to, a sensor unit or fuel sensor assembly(“FSA”) 100 having an onboard computer assembly (“OCA”) 102 coupled viaa data communication link 120 to at least one sensor 104 positionedwithin each of at least one respective fuel tank 64 for detecting fuelvolume, density, temperature, and/or quality as discussed in furtherdetail below with respect to FIGS. 21-28. In one implementation, the OCA102 may be partially or totally integrated with an onboard diagnosticrecorder (not shown) of tractor 24 as well as interconnected to the CANnetwork 103, as illustrated.

As shown most clearly in FIG. 4, the FSA 100 and, in particular, the OCA102, includes a processor 172, a memory 174, and various inputs andoutputs (“I/O”) 176 interconnected via a bus 180. Memory 174 ispreferably flash memory, effective for storing computer program codeexecutable by processor 172. At least one sensor 104 is preferablycoupled via link 120 to I/O 176 for providing to OCA 102 data signalsindicative of measured fuel volume. From this measured fuel volume, wellknown calculations can be made to determine density and quality as maybe obtained by also checking the pressure and temperature of liquidfuels such as gasoline and diesel fuel. Further inputs to OCA 102include data indicative of mileage of the tractor 24 received via line136 from an odometer 134 located within the cabin 48 or equivalentcomponent on tractor 24. In one implementation, OCA 102 I/O 176optionally includes an accelerometer 138, such as a three-axis,self-orientating accelerometer, which may provide data such as themotion, degree of incline, and event-related activity of tractor 24.Various compensational adjustments may be made to the data based on theaccelerometer readings, discussed further below with respect to FIGS.15A and 15B. In the illustrated implementation, the FSA 100 preferablyalso includes a Global Positioning System (“GPS”) 190 coupled to the OCA102 through I/O 176 for facilitating the generation of data relative tothe vehicle location and date/time. Data generated by OCA 102 may, aspreviously indicated, also include access to the controller area networkCAN which as previously indicated comprises a vehicle bus standarddesigned to allow microcontrollers and devices to communicate with eachother within a vehicle without a host computer. In another embodiment, asensor may optionally be provided to even more accurately measure fuelquality than the system as illustrated in FIG. 4, such as BTU-values orother quality characteristics that would assist in further determiningthe quality of the fuel. Data input, such as measured fuel volume, fueltemperature, fuel quality, mileage, accelerometer data, location,tractor identification, date and time, are referred to collectivelyherein as “fuel log data”. OCA 102 I/O 176 includes a transceiver 182coupled via a line 137 to an antenna 60 (FIG. 3) mounted in the cabin 48for transmitting fuel log data via network 28 to RS 16. The CAN system103 is also illustrated as communicating with the input output block176.

FIG. 5A is a flow chart of preferred steps performed by system 10 fordetermining the volume, and/or quality of a consumable, such as gasolineor diesel fuel, used, for example, in a vehicle whether or not in acommercial transportation vehicle fleet where the determination as towhether or not a fuel event has occurred is accomplished at the RSserver 16. Beginning at step 502, execution proceeds to steps 504 and506. At step 504, a driver of tractor 24 adds fuel purchased from a FDS20 to at least one tank 64 of his/her tractor. At step 512, the FDS 20generates and transmits fuel dispensed data 30 (e.g., invoice number,vendor, date and time, location, vehicle or driver identification,dispensed volume of fuel purchased, and total and per unit cost of thefuel) to IS 18 which, in step 514, forwards the data to RS 16 which, instep 516, saves the data to memory 204. As indicated supra, in someembodiments and locations of an FDS, block 514 is bypassed and the datafrom the tractor 24 is transmitted directly to the save data block 516in the RS 16. Returning to step 506, the at least one fuel sensor 104 ofFSA 100 generates one or more data signals indicative of one or more ofthe fuel pressure, density, volume, and fuel temperature, and transmitssame to OCA 102. OCA 102 then generates fuel log data, including fuelpressure, density, along with measured volume (and optionallytemperature), vehicle and/or driver identification, date/time, andlocation. In step 508, OCA 102 transmits the fuel log data to RS 16. Atstep 516, the fuel log data 32 is saved to memory 204 of RS 16. In step510, OCA 102 waits a predetermined length of time, such as thirtyseconds, and execution returns to step 506. As may be expanded uponlater, the “wait time” may optionally very depending upon theoperational status of the vehicle. In other words, if the engine is offand is at a location corresponding to where a driver might sleep or eat,the time may be extended too many minutes. On the other hand, if thevehicle is being refueled the length of time between determinations maybe reduced as indicated infra. Also, if it is detected that fuel volumeis decreasing faster than normal based on the detected operationalstatus of the vehicle, the time between volume detections wouldpreferably be reduced for the purpose of determining leakage or theft offuel from the fuel tank or fuel loss from accompanying fuel transmissionlines or severe engine operational factors.

It may be appreciated that there may be hundreds of transmissions offuel log data 32 from FSA 100 for each transmission of fuel dispenseddata from fueling FDS 20. Furthermore, in an alternative embodiment ofthe invention, fuel log data 32 may be accumulated in OCA 102 and nottransmitted to RS 16 until a predetermined quantity of data isaccumulated, until there is an increase in fuel volume (e.g., a fill-upor additional quantity of fuel appropriate to travel to a more desirableadditional energy source), a significant decrease in fuel is detected,or until the accelerometer 138 (or alternatively, GPS 190 or speedometer134) indicates that the tractor has stopped long enough (e.g., 30seconds, preferably a configurable time) to add fuel to its at least onefuel tank. Because fuel levels may vary due to motion, vibrations,sloshing in the tank, and the like, it is preferable to use rollingaverages of fuel volume calculated from averaging a predetermined numberof the most recent volume calculations each time a new measurement istaken. It may be preferable in many instances to reduce the increment oftime between measurements (e.g., from 30 seconds to 1 second) when fuelis being added to a tank (as may be determined as described above usingan accelerometer, GPS, or speedometer) so that more accuratemeasurements may be made during fill-ups.

Subsequent to saving fuel dispensed data 30 and fuel log data 32 at step516, execution proceeds to step 518 wherein a determination is madewhether there is a “fuel event.” A fuel event occurs when there is anon-trivial or unexpected increase or decrease (i.e., loss) in fuelvolume or quality, that is, an increase or decrease in fuel volume whichexceeds a predetermined threshold for a predetermined period of time.This can happen in at least the following three scenarios:

1. A decrease in measured volume reported by fuel log data 32, whichdecrease exceeds, by at least a predetermined threshold amount over apredetermined period of time, a decrease that would be expected from theconsumption of fuel by an engine, that is, that would be attributable tomileage or miles per gallon (“MPG”); this would indicate a fuel lossthat could result from, for example, leakage from a hole in a fuel tankand/or fuel system which could result in economical and environmentalimpacts (wherein execution would proceed to step 526, discussed below).In another example, a fuel decrease could result from fuel theft (e.g.,siphoning of fuel) (wherein execution would proceed to steps 524 and526, discussed below).

2. An increase in volume or quality reported similarly by both fueldispensed data 30 and fuel log data 32, i.e., a normal fill-up (whereinexecution would proceed to step 526, discussed below).

3. An increase in volume or quality, wherein the dispensed volume valuereported by fuel dispensed data 30 exceeds a measured volume of similarvalue reported by fuel log data 32 by a predetermined threshold for apredetermined period of time, in which case an alert is generated. Thisalert may indicate that a fueling station 20 ran up the number ofgallons on the transaction and gave a driver a monetary kickback. Thiscould also occur when a fueling station 20 up-charged a customer on aper/gallon basis (wherein execution would proceed to steps 524 and 526,discussed below).

Accordingly, a non-trivial fuel measured volume increase may occur whenthere is at least a start of a fill-up, rather than motion, vibration,and/or sloshing of fuel in a tank. A non-trivial fuel volume decreasemay occur when there is a theft by the siphoning of fuel from a tank,rather than for reasons attributable to miles per gallon (“MPG”) offuel. If, at step 518, a transmission of fuel log data is received thatdoes not indicate a non-trivial increase or decrease in fuel volume,then no fuel event is deemed to have occurred, and execution proceedsto, and terminates at, step 520. If, at step 518, a non-trivial increaseor decrease in fuel volume is detected, then a fuel event is deemed tohave occurred, and execution proceeds to step 522.

At step 522, if a non-trivial increase in measured fuel volume has beendetected, then there should also be corresponding fuel dispensed datahaving substantially similar date and time stamps for a respectivetractor 24. RS 16 attempts to identify such fuel dispensed data. If suchfuel dispensed data cannot be located, an indication of “zero” dispensedvolume may be recorded and a report of same is generated. If such fueldispensed data is identified, then the volume of fuel purchased iscompared with the volume of fuel logged and a difference is determined;execution then proceeds to steps 523 and 526. In step 523, adetermination is made whether the difference determined in step 522exceeds a predetermined threshold, such as a fuel loss greater than tengallons, a fuel temperature that rises more than a predeterminedthreshold or a fuel temperature that drops below 32° F. If it isdetermined that such threshold has been exceeded, then executionproceeds to step 524; otherwise, execution from step 523 terminates atstep 520. In step 524, the fuel dispensed data, fuel log data, anddifference is preferably transmitted via email to the workstation 12 forpresentation on display 13 and/or via text (e.g., Short Message Service(“SMS”)) to a user for instant notification.

It should be noted that in step 522, while it would be obvious if anontrivial decrease in measured fuel volume is detected there would beno corresponding fuel dispensed data, the same procedure is followed inchecking fuel dispensed data, and reporting the fuel event and a zeroindication of dispensed volume along with the measured volume of fueldecrease.

In step 526, upon login to workstation 12, a user is notified of thefuel event, preferably by a report on display 13 (discussed in greaterdetail below with respect to FIG. 7), or alternatively by a hard copyprintout. In step 528, the user preferably reviews the report anddetermines whether any action is necessitated, marking the reportaccordingly in step 530, the marking preferably including the date andtime of review, as well as the identification of reviewer. By way ofexample, if the difference between the dispensed volume of fuelpurchased (per fuel dispensed data 30) and the measured volume of fuellogged (per fuel log data 32) indicates that the amount of fuelpurchased was greater than the amount of fuel logged in the at least onetank 64, then fraud is suggested, and appropriate action may be takenagainst the driver to resolve the situation. Similarly, if a non-trivialdecrease in fuel occurs, suggesting that fuel has been siphoned off byway of theft, then appropriate action may be taken against the driver toresolve the situation. In step 532, the report, including any mark-ups,is saved in memory 204 of RS 16. Execution is then terminated at step520.

FIG. 5B is very similar to FIG. 5A in showing a flow chart foraccomplishing the same end result except that the fuel event isdetermined in the processor 102 of the FSA 100 rather than in RS 16,though RS 16 may be used to confirm a fuel event. Having the vehicletransmitting data only when the memory of FSA is substantially full orwhen a fuel event and/or other critical event (CE) requiring instantnotification has occurred substantially reduces the work at the remoteserver 16 and reduces the likelihood that a large number oftransmissions are trying to be received by the server 16 at the sametime. As shown, the process is designated as 550 and commences with thestart step 552. When the vehicle 24 is finished receiving fuel asdispensed at a FDS, the driver will submit the charge card to the FDSand the FDS will transmit the fuel dispensed data either to theintermediate server (IS) 18 or directly to the remote server 16 as setforth in steps 564, 566 and 568. The remote station 16 will save thedata received and await input from the vehicle 24.

As set forth in step 556, the FSA 100 will continuously determine fuellevel status and send this information to step 558 for collection andsaving and thus when fuel is added to the tank or deleted from the tankin amounts outside normal operational parameters, a fuel event isdetected as set forth in step 560. FSA 100 has a limited amount ofmemory available for storage of detected data. Prior to the time that afuel event or CE is detected, and as shown in step 558, if the amount ofdata in memory exceeds a predetermined threshold, FSA 100 may at anytime send data (e.g., in batches) to remote station 16 wherein it issaved as noted in step 570. When more than a given amount of fuel levelchange is detected by fuel sensor 104 in a given amount of time asdetermined by the computer 102, FSA 100 may immediately notify remotestation 16 that a fuel event (or possibly even a critical event such asan extreme loss of fluid while the truck is still moving) has beeninitiated and later send another notification that the fuel event hasbeen completed and send previously collected data in both instances. Onthe other hand FSA 100 may alternatively be programmed or designed tosend the fuel event notification only after the fuel level has stoppedchanging significantly and a given period of time has elapsed.

The processor 102 in FSA 100 may be programmed to only save and/ortransmit collected data to step 570 that it deems relevant (e.g.,indicative of a fuel event) depending upon operational circumstances. Inother words, on a long-distance trip with no abnormalities detected,even though it may collect data every few seconds, it may only save andstore the data every few minutes as long as nothing critical is detectedsuch as low temperature of the fuel or excessive change in volume orquality. Further, even though data may be saved and stored, theprocessor 102 may, according to given parameters, eliminate or otherwisenot transmit certain data that remains substantially identical to otherstored data. This elimination of data would certainly be realistic whenthe vehicle is parked for an entire night at a motel when the engine isinoperative and there has been no detection of fuel level change orsignificant temperature change for the entire night and no othercritical event situations are detected.

Once the remote station 16 has received a determination of a fuel eventor receives other critical event information, the fuel dispensed data isreconciled in step 572 before the program proceeds to decision step 574.If no CE or threshold is noted the program proceeds to step 586 wherethe RS 16 waits until a more data is received or a fuel event or CE isreceived as shown in steps 568 and 570. The data from step 572 is alsosent to step 578 to notify the user of the fuel event. The programproceeds to step 580 where the user reviews the fuel event, marks it asillustrated in step 582 and the data is saved in step 584 beforeproceeding to the wait step 586. As also shown, if a critical eventnotification is received or a threshold is exceeded, as determined indecision step 574, the process to step 576 whereby instant notificationis provided as previously indicated in connection with FIG. 5A.

FIG. 6 illustrates seven categories or modules 220 of forms, reports,and functions 222 available from RS 16 upon execution by processor 202of computer program code stored in memory 204 for keeping track of aconsumable, such as fuel. The modules 220 are preferably accessible viamenu buttons such as exemplified proximate to the upper right portion ofthe forms and reports described here. As discussed in further detailbelow, the modules 220 include a dashboard module 224, a user module226, a reporting module 228, a logs module 230, a configure module 232,a help module 234, and an instant notification module 236. These menuitems are preferably accessible via software “buttons” provided on theforms and reports described herein, and exemplified proximate to theupper portion of each form and report described herein.

More specifically, and with reference to FIG. 7, the dashboard report238 is preferably the first screen a user sees when he or she logs ontoRS 16, and preferably provides up-to-date, real-time information aboutthe system 10. By way of example and not limitation, the dashboardmodule 224 preferably supports the generation and presentation of adashboard report 238 that includes date/time, recent fuel events (e.g.,fuel tank fill-ups), real time inventory, fuel loss events, graphicaltrend charts, and a number of frequently used, pre-defined reports, asdiscussed in further detail below.

Recent fuel events, also referred to as fuel purchase reconciliationsand discussed above with respect to steps 518 and 522 of FIG. 5A,present both fuel dispensed data 30 with fuel log data 32, related bycommon data including date, time, and preferably unit, or tractor, ID.Fuel dispensed data 30 preferably also includes invoice number, thenumber of gallons purchased, and the retail price per gallon (“PPG”).Fuel log data 32 preferably further provides measured gallons received.Then, as also depicted by step 522 of FIG. 5A, discussed above, gallonspurchased is compared with gallons received, and the difference, alsoreferred to as a reconciliation, is presented. If a user clicks on arow, or record, of the fuel purchase reconciliations, an event detailsreport 239 pops up, as exemplified in FIG. 8. It is considered that theinformation depicted in FIG. 8 is self-explanatory and, therefore, doesnot warrants detailed discussion. While the dashboard report 238 asexemplified only displays recent fuel events, fuel event data for anydate range is available from the Fuel Purchase Reconciliations Report242, available under the reporting module 228 and exemplified by FIG.10.

The dashboard report 238 further preferably includes recent Vehicle FuelI data, which provides current information about the status of fuel infuel tanks 64. Such information preferably includes not only currentgallons of fuel available for each tractor 24, but also the temperatureof the fuel in each tank 64 of tractor 24. Fuel temperature is importantto monitor because, as fuel gets cool under cold-weather conditions, itmay begin to approach a gel state, wherein the viscosity of the fuelbegins to change which can have a significant detrimental impact on theperformance of an engine. As such, RS 16 notifies a user when thetemperature of the fuel is approaching a gel-like state so that thedriver can take proactive steps (e.g., add an additive to the fuel orswitch to a different fuel) to prevent or prepare for such a situation.While the dashboard report 238, as exemplified, only displays recentfuel inventory data, fuel inventory data for any date range is availablefrom the Vehicle Fuel Report 244, available under reporting module 228and exemplified by FIG. 11.

Still further, dashboard report 238 preferably also reports recent fuelloss events, that is, a non-trivial decrease in fuel that is notaccountable by use of fuel by the tractor 24, but is possibly due tofuel theft, such as siphoning of fuel from a fuel tank. If there is sucha fuel theft event, then the user will be notified by the dashboardreport. As discussed above with respect to step 524 of flow chart 500(FIG. 5A), a user and respective driver are notified immediately of suchtheft via email and/or SMS text messaging. While the dashboard report238 as exemplified only displays recent fuel loss events, fuel loss datafor any date range is available from the Fuel Loss Events report 246,available under reporting module 228 and exemplified by FIG. 12.

The dashboard report 238 preferably also includes graphical trendcharts, including charts showing the average number of fuel events inrecent months, what proportion of fuel events are considered normal, ofmoderate concern, and of critical concern. Charts are preferably alsoprovided showing fuel expenses for recent months, as well as averageprice per gallon of fuel for recent months.

Access to other pre-defined reports that are frequently used are alsoprovided. By way of example, pre-defined reports may include reports ofcritical (e.g., auditable) events by city, state, driver, and/or truckfor the past month, year, or other selected time period. Pre-definedreports may further include reports of the percentage of fuel purchases(by vehicle) resulting in a critical event, or of fuel purchases madethe previous day, for example. An event report may be generated to showfuel purchase reconciliations for a pre-determined time period, such asyear-to-date, or a rolling previous period, such as the previous six ortwelve months. This would allow a user to easily access all suchtransactions rather than having to wade through the reporting menu andsearch for them.

Under user module 226, a user, preferably limited to an administrativeuser, may access a User Access Configuration report 240. As shown mostclearly by FIG. 9, the user access configuration report identifies allusers who have access to RS 16, preferably including their respectiveuser name, email address, access group or privilege, and the last timethey logged onto RS. Through the User Access Configuration report, auser with administrative rights may control who has access to RS 16 byadding users, removing users, and establishing and modifying userprofiles, including their security rights, also referred to asprivileges. By way of example, two security profiles are depicted inFIG. 9: (1) a “system administrative” profile, which has norestrictions, and (2) a “viewer” profile, which is limited to viewingforms and reports, but not entering or editing any data on them.

Under the reporting module 228, three reports 242, 244, and 246 (FIGS.10-12) are available, which report similar data as discussed above withrespect to dashboard 238, but which cover any date range selectable by auser. The substance of these reports has been discussed above, andtherefore will not be discussed in further detail herein.

Under the logs module 230, two reports are available: (1) a raw fuel logdata report (entitled “Daily Fuel Logs”) 248 and (2) a raw fueldispensed data report (entitled “Fuel Purchase Logs”) 250, exemplifiedby FIGS. 13 and 14, respectively. The raw fuel log data report 248reports fuel log data 32 that is received from the OCA 102, and the rawfuel dispensed data report 250 reports fuel dispensed data 30 that isreceived from the IS 18 or fueling station 20. Data in reports 248 and250 is used in other reports, such as the dashboard report 238, thethree reports 242, 244, and 246, as well as the process depicted in flowchart 500 discussed above with respect to FIG. 5.

Configure module 232 preferably includes at least six forms 252-262 thatenable users to configure various aspects of RS 16. A Fuel ProbeConfiguration form 252, exemplified by FIGS. 15A and 15B, enables a userto configure and customize the settings of individual fuel probes, orgroups of probes, also referred to herein as fuel sensors, 104. Theseconfigurations are then sent to the unit (e.g., tractor 24), allowingfor substantially real-time updates to be made to sensors 104. As shownon FIGS. 15A and 15B, some of the settings constituting theconfigurations include the following:

IP Address: for the tractor 24

Status Update Time: how often (preferably in hours) a tractor 24transmits a report to RS 16, the report including fuel log dataaccumulated subsequent to a last transmission, fuel log data preferablyincluding pressure and temperature readings, GPS data, accelerometerdata, and date/time stamps

Pressure steady count: number of counts (i.e., units of measurementarbitrarily chosen for convenience in using the invention) in pressurethat are considered to be slight variations that are not taken intoaccount when assessing whether or not there has been a fuel event (e.g.,a fill-up or fuel loss)

Log time interval: how often (preferably in seconds) fuel log data 32 iswritten to memory 174 of the OCA 102 (i.e., sample rate)

X, Y, Z change: the threshold amount of change allowed in the X, Y, or Zdirections of the accelerometer 138 before it is considered to indicatemovement of the tractor 24

estartrig: the threshold for number of increase or decrease counts thatwill trigger the start of a fuel add or loss event, respectively

estoptrig: the threshold for number of increase, decrease or steadycounts that will trigger the end of a fuel add or loss event

esamples: the number of pressure samples in the event averaging buffer

echangetrig: the pressure change threshold that is considered to resultfrom a “change in pressure” rather than random movement of fuel, such assloshing

esteadyclear: the number of times a pressure change less than“echangetrig” that will clear the up/down change counters

esloshcount: the number of seconds to wait after movement of the tractor24 has been detected before starting all event counters, that is,configuration variables that have to do with how the fuel events (e.g.,fill-ups or fuel losses) are detected and processed

geltemp: the temperature at which fuel begins to gel

Tank Size: size of the tank (e.g., in gallons)

Pressure when full: total pressure reading when tank 64 is full

Pressure per inch: reading from the sensor 104 that will be consideredan inch of fuel

Pressure adjust: a value always added to pressure readings from thesensor 104 to account for pressure sensors being slightly off the bottomof a tank 64

It is considered that the use of the above-identified variables andsettings in the system 10 of the invention would be apparent to a personhaving ordinary skill in the art upon a reading of the description ofthe invention herein, and therefore will not be described in furtherdetail herein, except to the extent necessary to describe the invention.

A Fuel Purchase Report Configuration form 254, exemplified by FIGS. 16Aand 16B, enables a user to configure the fuel purchase reports, whichare used for fuel event reconciliations against raw fuel log data. Theuser may manage how fuel dispensed data 30 is imported from intermediateserver (IS) 18 to RS 16 by configuring automated data downloads from IS18, either in real time or periodically (e.g., in nightly batches), orby manually downloading charge card data in spreadsheet format from IS18 to workstation 12 followed by upload (via form 254) of spreadsheetfrom workstation 12 to RS 16.

As will be apparent to those skilled in the art, in systems where all orpart of the FDS's 20 report directly to RS 16, the server at these FDSscould be programmed in the same manner. Optionally, since such aconnection would typically be landline, each transaction could betransmitted directly to RS 16 as it occurred.

A Report Configuration form 256, exemplified by FIGS. 17A and 17B,enables a user to configure customized reports, including the contentthereof, using data collected and stored by the system 10. Such reportsmay preferably be generated on an ad hoc basis or may be scheduled to begenerated on a recurring basis.

An Alerts Configuration form 258, exemplified by FIGS. 18A and 18B,enables a user to configure instant notifications, or alerts. A userpreferably has the option to configure at least fuel loss and/ortemperature alerts which can be sent to the user, such as by way ofemail or SMS (e.g., text) message. Alerts may be grouped by units (e.g.,tractors 24) and sent to one or more email or SMS recipients, including,by way of example but not limitation, the workstation 12 and the OCA 102of the subject tractor 64, which OCA could display the alert on thetractor's dashboard and/or instrument panel (e.g., by illuminating thefuel gauge light).

A Product Configuration form 260, exemplified by FIG. 19, enables a userto configure different product types of fuel sensor 104. This formenables a user to set a product code and description for each producttype which is then used to further group and configure individual fuelsensors.

A Firmware Updates form 262, exemplified by FIG. 20, enables firmwareupdates to fuel sensors to be sent globally to fuel sensor assemblies100.

The help module 234 includes About Us function 264 and a Help Menufunction 266 which provide various types of support to the user. Suchfunctions are considered to be well known in the art and so will not bediscussed further herein.

The instant notification module 236 includes Email form 268 and SMS form270 which enable a user to configure how emails and text messages aresent, preferably in real time. By way of example, but not limitation,such an email to display 13 or text to a cell phone may be sent in step524 of the process depicted by flow chart 500 of FIG. 5, or when a fuelloss event has been identified.

It should be appreciated that although particular flow diagramarchitectures are shown and described in connection with FIGS. 5A and5B, other architectures are within the teachings presented herein. Byway of example and not limitation, additional modules may be included.For example, a data input configuration module may be included toprovide further capabilities to a user to set-up data inputs, which willallow various reconciliations to occur. Various fuel data and purchasedata functions may be configured. Specific software handlingcharacteristics such as file handling, parsing, and file formatting maybe handled by a given module. Mapping functionality may be incorporatedinto the various modules presented herein such that information isoverlaid onto a map.

It can be appreciated that RS 16 is able to accumulate substantial datafrom the system 10, whether partially generated initially within FSA 100or mostly generated within server 16, about travel between variousroutes between points, such as cities. Such data may include vehicleperformance, such as average miles/gallon, average speed, and averagetravel time. Data about the various routes may also include currentprice/gallon of fuel at various fueling locations. With this data, RS 16may propose an optimized route based on an optimization characteristicor a weighted combination of characteristics, such as length of route,time to travel a route, and the cost and quality of fuel along arespective route, as exemplified below with respect to FIG. 21.Additionally, RS data may be used to provide a database of all fuel andtravel data from a fleet of tractors. For example, if a user (e.g., anauditor, manager, attorney) needs to research characteristics of a truckat a given point in time, the database could be searched for thatinformation (e.g., fuel level, GPS location, temperature of the fuel,and truck characteristics such as MPG, mileage, and the like). Likewise,the RS database also stores all the fuel purchase reconciliation datawhich may be of use to an auditor who performs quarterly or yearlyaudits on fuel purchases.

FIG. 21 exemplifies one scenario of a fuel optimization application ofRS 16 of system 10. Tractor 24, employing the systems and processespresented herein, is hauling a load 26. As shown, city 384, fuelinglocation 386, city 388, city 390, city 392, fueling location 20, andfueling location 22 are interconnected by highways 394, 396, 398, 400,402, 404, 406, 408, 410, and 412. The transportation carrier frequentlyhas tractors hauling freight on the route between city 384 and city 390.As a result, RS 16 has collected data about the various routes betweencity 384 and city 390. For example, one route may be city 384, which isthe origin, on highway 394 to fueling location 386, on highway 396 tocity 388, and on highway 398 to city 390, which is the destination.Another route may be city 384 on highway 404 to fueling location 20 onhighway 402 to city 392, and on highway 400 to city 390, which is thedestination. Yet another route may be to city 384 on highway 406 tofueling location 22, on highway 412 to city 392, and on highway 400 tocity 390. While there are thus a number of routes that could be taken,using data that RS 16 has accumulated, an optimized route may beproposed for tractor 24 hauling freight 26 from city 384 to city 390based, for example, on the price/gallon of fuel or, if the quality ofthe fuel is known, the price per BTU (British Thermal Unit). Therefore,as shown, tractor 24 utilizes highway 404, fueling location 20, highway402, and highway 400 to city 390.

FIG. 22 depicts a side view of the tank 64 described above andconfigured for storing fluid 1001, such as fuel, such as diesel fuel orgasoline. Except as described herein, tank 64 is generally aconventional fuel tank, including a fuel supply line 96 extending froman outlet 98 to an engine (not shown) and, for fuel such as diesel fuel,a fuel return line 94 entering an inlet 92. To the extent that tank 64is a conventional tank, it will not be described in further detailherein, except to the extent deemed necessary to describe the invention.

As shown by way of a broken-away portion of a side wall of tank 64, anopening 1016 is formed in the top of tank 64. A cylinder 1002 extendsthrough opening 1016. Cylinder 1002 includes a ring plate 1020configured for extending across opening 1016 and supporting cylinder1002 in tank 64. Plate 1020 is preferably secured to tank 64 in anyconventional manner, such as by fasteners, such as screws and/or bolts,or welding, and preferably with a gasket to act as a seal effective forpreventing leakage of fluid 1001 from within the tank. Cylinder 1002 ispreferably configured with vent holes 1003 for equalizing pressurebetween the interior and exterior of tank 64 as fuel volume changesand/or as altitude and atmospheric pressure changes. A tube 1004 extendsthrough cylinder 1002, and sensor 104 is attached to a lower end of thetube to thereby position sensor 104 in fluid 1001.

As shown in FIG. 23, pressure sensor 104 is preferably a differentialpressure sensor having electrical circuitry 150 including a processor152 and a memory 154 effective for storing computer program codeexecutable by processor 152. As is known by those skilled in the art,differential pressure sensors are available on the market with not onlya processor and memory, such as illustrated, but may optionally alsoinclude a temperature sensor and heater (not shown). When a temperaturesensor and heater are included, processor 152 is programmed to activatethe heater to maintain at least a minimum operating temperature ofsensor 104, including pressure detector 112, whenever the temperature ofthe fluid being measured drops below a given value to eliminate at leastpressure sensing problems that may occur if the fluid is proceedingtoward a solidified state. A bus 160 is provided which couples togetherprocessor 152 and memory 154, as well as an input/output (“I/O”) 156.Sensor 104 further includes a pressure detector 112 and, optionally, atemperature detector 138, both of which detectors are coupled toprocessor 152 and memory 154 via I/O 156 and bus 160. Processor 152 iseffective for receiving signals from pressure detector 112 and,optionally, temperature detector 138, and generating signals indicativeof pressure and temperature, respectively, onto I/O 160, fortransmission via respective electrical signal lines 1010 and 1012 to OCA102, which transmits the signals to RS 16 for use in step 506 of theprocess 500 depicted in FIG. 5A or process 556 of FIG. 5B. It is notedthat the term “sensor” as used herein may comprise a single detector ormultiple detectors.

Sensor 104 preferably also includes a vent line 1014, which runs throughtube 1004 (FIG. 24) and outside tank 64 to a dry box 1018 forcommunicating atmospheric pressure to sensor 104. In one embodiment, asdiscussed above, sensor 104 is a differential pressure sensor. It iswell known that differential pressure sensors are effective formeasuring the difference between two pressures, one connected to eachside of the sensor, and therefore will not be described in furtherdetail herein except insofar as necessary to describe the invention.Accordingly, fuel pressure is connected to one side of the differentialpressure sensor and atmospheric pressure is connected to the other sideof the differential pressure sensor. The differential pressure sensorthen generates a signal to processor 152 indicative of the fuel pressureless the atmospheric pressure. Effectively, then, measured fuel pressureis simultaneously and continuously adjusted by atmospheric pressure, sothat processor 152 does not need separately to account for the effectsof atmospheric pressure on the pressure of fluid 1001 in the tank 64when determining volume. Thus, in the embodiment illustrated, thepressure indicative signal output by the sensor 104 is alwayscompensated for the effects of changing atmospheric pressure applied tothe surface of the fluid in the tank regardless of geographic altitudeand changes in the weather affecting barometric pressures.

As will be realized, the calculation of volume by the processor is alsoobtainable by using a fluid pressure signal received from a fluidpressure sensor such as 104, and using a processor (e.g., 152 or 172) toadjust (i.e., reduce) the value of that fluid pressure signal by anamount indicative of an atmospheric pressure signal received fromanother source, either inside or outside of tank 64, before volume isdetermined by processor 152 or, alternatively, by a processor outside oftank 64, such as processor 172 (FIG. 4).

It may be appreciated that fluid 1001 in a moving tractor 24 will slosharound, vibrate, and move from one end of tank 64 to the other as theangle of the tractor changes, such as when traveling up or down anincline, such as a hill. As fluid 1001 moves, the pressure sensed bypressure detector 112 may fluctuate, potentially resulting in erroneousmeasurements. To dampen such fluctuations, a mesh buffer 113 ispreferably incorporated in pressure detector 112 by being positioned inor over the input port of the pressure detector 112. A mesh bufferpreferably comprises a soft, porous material such as cellulose woodfibers, foamed plastic polymers, or the like.

Dry box 1018 includes desiccant to aid in absorbing moisture and keepingair in vent line 1014 dry so that atmospheric pressure may be accuratelycommunicated. Dry box 1018 may be located in any suitable place that isconvenient and protected from water in the environment, such asprecipitation (e.g., rain) and water that splashes up from a roadway.Dry box 1018 may, for example, be located in cab 48 and/or integratedwith OCA 102 (which may also be located in cab 48).

Sensors that detect pressure and temperature are considered to bewell-known and commercially available from manufacturers, and so willnot be described in further detail herein, except insofar as necessaryto describe the invention.

As shown most clearly in FIG. 24, in a cross-section of tube 1004 takenalong line 24-24 of FIG. 22, tube 1004 carries the lines 1010 and 1012as well as the vent line 1014. As shown in FIG. 22, the tube 1004extends through cylinder 1002 to the exterior of tank 64. Outside oftank 64, electrical signal lines 1010 and 1012 are preferably carriedwith the data communication link or tube 120 in any suitable manner,such as by way of split loom tubing, to processor 172 of OCA 102. In oneembodiment, depicted by FIG. 22, outside the tank 64, vent line 1014 isseparated from tube 120 carrying electrical signal lines 1010 and 1012,and is directed to dry box 1018. In an alternative embodiment, dry box1018 is integrated with OCA 102 and vent line 1014 is carried by tube120 with signal lines 1010 and 1012 to dry box 1018 in OCA 102.

In a preferred embodiment of the invention, a compensatory pressuredetector 1005 is positioned above sensor 104 by a space 1007 to moreprecisely determine density (or an analogue thereof) to thereby obviateerrors that may result from a change in density due to, for example,varying grades of fuel, water from condensation or fraud or the effectsof temperature on fluid 1001. Additional electrical signal lines 1010(not shown) are preferably provided from compensatory pressure detector1005 to processor 152 for processing and then transmission via bus 160and I/O 156 to OCA 102. Alternatively, additional electrical signallines 1010 may be provided for carrying signals from detector 1005 intube 120 to OCA 102. In the preferred embodiment, memory 174 in OCA 102is preferably provided with computer program code for comparing thepressure measured by pressure detector 112 and the pressure measured bycompensatory pressure detector 1005, and determining a difference, ordelta pressure. The delta pressure may be used to determine density (oran analogue to density) of fluid 1001, and thereby determine moreprecisely, with the pressure measured from pressure detector 112, theheight of fluid in tank 64, from which height the volume of fluid intank 64 may be determined. In one embodiment of the invention, suchcalculation may be made using the following variables:

W_comp=compensated liquid weight value per inch of liquid

C_distance=compensation distance setting, designated by referencenumeral 1007 in FIGS. 22 and 26.

T_distance=calculated total liquid height in tank.

P_primary=pressure reading from primary sensor, exemplified by sensor104

P_comp=pressure reading from compensating pressure sensor 1005.

The above variables may then be used in the following equations tocalculate T:

W_comp=(P_primary−P_comp)/C_distance

T_distance=P_primary/W_comp

Exemplifying with specific values, such as P_primary=5 psi, P_comp=3psi, and C_distance=4 inches, then:

W_Comp=5 psi−3 psi/4 inch=0.5 psi per inch

T_distance=5 psi/0.5 psi=10 inches of liquid in the tank.

It is considered that such equations to effectuate such calculations anddeterminations would be apparent to a person having ordinary skill inthe art upon a reading of the present description herein, and so willnot be described in further detail herein. The density is preferablycalculated only when tank 64 is filled up, and then stored in memory 154until a subsequent fill-up or optionally a loss sufficient to triggerthe determination of a fuel event, thereby avoiding errors incalculations when the level of fluid falls below the level of thecompensatory pressure detector 1005.

As noted above, pressure readings are subject to fluctuations due to anumber of factors, for which a buffer mesh was disclosed for dampeningthe fluctuations. To further smooth the effects of pressure fluctuationsand obtain still more accurate measurements, the pressure is preferablymeasured frequently (e.g., every 30 seconds) and a rolling average isgenerated, representing a more accurate measurement of fluid pressureand, hence, fluid volume, as discussed above with respect to steps506-510 of the flow chart 500 of FIG. 5A or steps 556-560 in FIG. 5B.

To obtain further enhanced accuracy of fluid pressure and volume,particularly when fluid shifts from one end of tank 64 to the other, inan alternative embodiment of the invention, multiple pressure sensorsare used proximate to the bottom of tank 64, and measurements from themultiple pressure sensors are averaged. Accordingly, FIG. 25 exemplifiesan alternative embodiment of the invention in which two pressure sensorsproximate to the bottom of the tank 64 are utilized, preferably inaddition to the compensatory pressure detector 1005, described above. Inaddition to pressure sensor 104, an additional sensor 1006 is utilizedto measure fluid pressure, and hence, volume, more accurately. Sensor1006 includes a pressure detector 1007 preferably substantially similarto pressure detector 112, and includes circuitry similar to circuitry150 of FIG. 23. It is not necessary that sensor 1006 be provided with atemperature detector as the sensor 104 was optionally provided with thea temperature detector 138. However, if both sensors include temperaturemeasurement, the two can also be averaged for more accuracy sincetemperature of fluid on one end of a container is not always identicalwith temperature at the other end. Pressure detector 1007 is preferablycoupled to a processor via lines running through I/O and a bus, and thenonto an additional set of electrical signal lines 1010 to OCA 102. In analternative embodiment, all electrical signals indicative of pressureand/or temperature are combined by a single processor and transmittedvia a single pair of lines to OCA 102 using conventional serialcommunication technology, as is well known in the art.

Further to the embodiment of FIG. 25, tube 1004 is replaced by an uppertube 1024, a splitter 1026, and two tubes 1004 a and 1004 b, withreinforcing tubing 1030, terminating in sensors 104 and 1006,respectively. Tubes 1004 a and 1004 b are preferably of dissimilarlengths so that sensors 104 and 1006, when together as shown in FIG. 25,maintain a smaller lateral (or horizontal) profile so that they may bepassed more readily through opening 1016. A spring 1052 is preferablypositioned on the two tubes 1004 a and 1004 b for spreading the twotubes apart, preferably by an angle of about 180°, as more clearlydepicted in FIG. 26. In operation, when pressure measurements aredesired, fluid pressure is measured from both pressure detectors 112 and1007 and preferably averaged, and the average value is used, forexample, in step 508 of FIG. 5A or step 560 of FIG. 5B, as well as indetermining the density of the fluid 1001 in conjunction with thecompensatory pressure detector, as discussed above. Operation of theembodiment of FIGS. 25-26 is otherwise similar to operation of theembodiment of FIGS. 22-24.

It may be appreciated that when tubes 1004 a and 1004 b, as well assensors 104 and 1006, are spread apart, it would be desirable that theymaintain a relatively constant position and orientation with respect toeach other, to facilitate consistently accurate and reliable fluidpressure measurements. To that end, FIGS. 27 and 28 exemplify asub-assembly of linkages 1042 and 1044 which are preferably adapted tothe embodiment of FIGS. 25 and 26, pivoting on the splitter 1026 andeach of reinforcing tubes 1030. FIG. 27 demonstrates how tubes 1004 aand 1004 b are substantially parallel, in solid outline, and move to aspread position in which tubes 1004 a and 1004 b are substantiallycollinear, in dashed outline. The latter position is shown in solidoutline in FIG. 28.

It may be further appreciated that by knowing the depth (or height) offluid 1001 in a tank 64, and the size and shape of a tank, the(measured) volume may be calculated in any of a number of different waysby OCA 102 processor 172, RS 16 processor 202, or any other suitableprocessor. By way of example but not limitation, the sensor 104 pressureoutput allows fluid volume to be calculated mathematically usingwell-known equations, given the size and shape of a tank for a givenfluid depth. In another example, fluid volume may be calculatedmathematically for a number of different fluid heights and a chartgenerated correlating height to volume; then a specific volume may bedetermined from the chart for any specific depth. In another example,volume amounts or values may be determined by manually pouring fluidinto a tank, one unit (e.g., gallon) at a time, and measuring thepressure or depth with each unit added and generate a chart from that.In another example, if tanks can be categorized into a few fundamentalshapes, the only variable being size, a chart may be generated for eachcategory of shape, and scaled for the size of any particular tank ofthat shape. Volume may also be scaled or adjusted for the density and/ortemperature (which affects density) of the fluid. It is considered thatfurther details exemplifying such methods, as well as alternativemethods, for determining volume of a fluid from variables, such aspressure or depth of the fluid in a tank and density of the fluid, wouldbe apparent to a person having ordinary skill in the art, upon a readingof the description of the invention herein; therefore, it is deemed notnecessary to discuss same in further detail herein.

As is well known, the amount of usable energy obtained from a givenenergy source is dependent upon multiple factors. For a liquid energysource such as diesel fuel, gasoline, propane, LNG, LPG, and so forth,the amount of usable energy available, such as BTU (British ThermalUnit) per volumetric unit, such as a gallon, is dependent upon not onlythe temperature of the liquid but also upon the quality of materialsused to formulate that liquid. Both diesel fuel and gasoline may haveadditives mixed in with the primary fuel that are derived from otherthan refined petroleum. Examples may be grain alcohol such as ethanolfrom harvested corn as applied to gasoline as well as biofuel productsrecovered from oils or fats such as in cooking greases that are added todiesel fuel. These additives are utilized for multiple political andeconomic reasons; however, both of these additives reduce the usableenergy (BTU) per gallon of the fuel as compared to the primary fuelwithout additives. However, diesel fuel as well as gasoline withoutadditives will vary in usable energy per gallon depending on the wellfrom which petroleum was derived, the manner in which it was processedin the refinery as well as to some extent the manner in which the fuelis stored before being used. Thus, every time a vehicle adds liquid fuelfrom a different energy source from previous refueling, the amount ofusable energy per gallon in the fuel tank is likely to change.

From a trucking company's standpoint, it is important to have somecomprehension of the amount of usable energy per gallon of fuel obtainedfrom any refueling source such as a truck stop or gas station. From adriver's standpoint the amount of usable energy per gallon is importantin determining how soon it will be necessary to add additional fuel tothe vehicle. Thus, it is advantageous to be able to measure the qualityof fuel obtained not only for the above reasons but to detect potentialfraud occurring in the delivery of fuel to the vehicle fuel storagecontainer. It is known that some fuel dispensing entities have engagedin a practice of heating the fuel to be dispensed to customers. Theheated fuel expands substantially in volume thus lowering the usableenergy BTUs available per received gallon of fuel. Thus, a customerreceiving heated fuel is paying more per gallon of received fuel (i.e.,more per BTU) than would be indicated or shown on the pump or invoice.

It would therefore be prudent, by determining the temperature ofincoming fuel being received by the one or more fuel tanks of a truck,to initially at least generate a rough guesstimate of the usable energybeing received at a given truck stop. If the source of a liquid fuel atthat station is below ground level, as it is in most commercialrefueling stations, and the temperature of the fuel being received isabove temperatures normally recorded at that truck stop or at othersimilar truck stops, it would be desirable to generate an alert messageto appropriate individuals for possible fraud. Even if the source ofliquid fuel is above ground, a substantial rise in temperature of fuelin the truck fuel container upon receiving fuel would (or at leastshould) raise suspicions of fraud since the fuel container in the truckis typically subject to the same ambient temperature as a truck stopabove ground source fuel container.

As mentioned elsewhere in the specification the one or more fuel sensorsin a given fuel tank include temperature sensing capability and therecording of this temperature is shown in various figures such as FIG.11. While an additional temperature sensor could be used to directlymeasure the temperature of incoming fuel T_(a) to the vehicles fueltank, the temperature of incoming fuel can reasonably accurately bedetermined by maintaining a record of the volume of fuel in the fueltank and the temperature of that fuel before adding new fuel at arefueling station. Then the temperature of the fuel added T_(a) may becalculated by the formula T_(a)=(V_(t)*T_(t)−V_(i)*T_(i))/(V_(t)−V_(i))where V_(t) is the total volume of fuel in the container aftertermination of incoming fuel, T_(t) is the temperature of the totalvolume as measured after termination of incoming fuel, V_(i) is theinitial volume measured before fuel is added and T_(i) is thetemperature of the initial volume of fuel before fuel is added. Whilethe calculated temperature density may not be exactly identical to thetemperature of the fuel as it passes through the measuring device in thefuel dispensing machine due to ambient temperatures affecting thecontents of the vehicle fuel tank, it is close enough to ascertainwhether or not fraud is involved and may be used to provide an initialindication to the vehicle driver or to other appropriate authorities howmuch usable energy is now available to operate the vehicle.

Once the vehicle is again moving on the highway the miles per gallon mayagain be computed for the vehicle utilizing the combined fuel quantitiescompared to the miles per gallon detected prior to adding fuel. Thisinformation may be used to obtain an even more accurate determination ofthe quality of the fuel obtained from the just used truck stop in amanner similar to that used above to obtain the temperature of the fueladded. Thus, over a period of time the accumulated information as tofuel quality from various refueling stations can be used to determinewhich stations to avoid for reasons either of fuel quality or potentialfraud.

Other energy sources that may be available for use by transportationvehicles may also have shortcomings relative to consistent qualityusable energy from an energy supplier. The wireless transfer ofelectrical energy through electromagnetic means to a vehicle requiringadditional energy is believed to be affected by not only otherelectromagnetic transmissions in the vicinity of the vehicle but also byweather conditions existing at the time of attempted transfer.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

1. A system for determining volume of fluid in at least one tank, thesystem comprising: at least one tank mounted on a vehicle, the at leastone tank being capable of storing a volume of fluid; at least onedifferential pressure sensor positioned within the at least one tank,and submersed in fluid when fluid is in the at least one tank, the atleast one sensor being configured for measuring pressure of fluidproximate to the bottom of the at least one tank; at least one vent lineoperably connected to the at least one differential pressure sensor, theat least one vent line having a single end through which air may flowand atmospheric pressure may be communicated to the at least one sensor,the at least one sensor being further configured for generating adifferential pressure output signal indicative of the fluid pressureless the atmospheric pressure; and at least one processor coupled to theat least one differential pressure sensor and operable for determiningthe volume of fluid from a received indication of the differentialpressure output signal.
 2. The system of claim 1, further comprising abuffer mesh positioned on the differential pressure sensor.
 3. Thesystem of claim 1 wherein the at least one sensor is also configured formeasuring temperature of the fluid and generating a signal indicative ofthe temperature to ascertain whether fuel frost or freeze event couldoccur.
 4. The system of claim 1 further comprising a memory coupled tothe at least one processor, the memory including computer program codeexecutable by the at least one processor for determining the volume offluid with reference to the pressure and density of the fluid and inaccordance with the size and shape of the at least one tank.
 5. Thesystem of claim 1 further comprising: a transmitter communicativelycoupled for receiving data signals from the at least one processor,mounted on the vehicle and configured for transmitting data signals to aremote server (RS); and a memory coupled to the at least one processor,the memory including computer program code executable by the at leastone processor for: determining the volume of fluid with reference to thepressure and the density of the fluid; and causing the transmitter totransmit data signals indicative of the volume of fluid to the RS, theRS being configured for receiving and processing the data signals. 6.The system of claim 1 further comprising: a transmitter, configured fortransmitting data signals to a remote server (RS, the transmitter beingcoupled to the at least one processor of the at least one sensor; and amemory coupled to the at least one processor, the memory includingcomputer program code executable by the at least one processor for:determining the volume of fluid with reference to the pressure and thedensity of the fluid; and causing the transmitter to transmit datasignals indicative of the volume of fluid to the RS, the RS including afurther processor and second memory coupled the further processor forexecuting computer program code for determining if fuel volume hasincreased more than a predetermined threshold and for generating analert if it is determined that fuel volume has changed in volume morethan a predetermined threshold.
 7. The system of claim 1 furthercomprising: a transmitter, configured for transmitting data signals to aremote server (RS), the transmitter being communicatively coupled to theat least one processor of the at least one sensor; and a memory coupledto the at least one processor, the memory including computer programcode executable by the at least one processor for: storing each datumindicative of a determined volume of fluid in memory; executing computerprogram code for determining if fuel volume has changed in volume bymore than a predetermined threshold; generating an alert if it isdetermined that fuel volume has changed by more than a predeterminedthreshold; and causing the transmitter to transmit an indication of thealert to the RS.
 8. The system of claim 1 further comprising: atransmitter, configured for transmitting data signals to a remote server(RS), the transmitter being coupled to the at least one processor of theat least one sensor; and a memory coupled to the at least one processor,the memory including computer program code executable by the processorfor: storing in memory the volume of fluid with reference to thepressure of the fluid; and causing the transmitter to transmit datasignals indicative of at least one of the determined volume of fluidstored in memory and/or an alert when it has been determined that fuelvolume has changed in volume by more than a predetermined threshold. 9.The system of claim 1 wherein the at least one sensor also includes atemperature sensor and a heater communicatively coupled with the atleast one processor and is configured for measuring temperature of thefluid and activating the heater when the measured temperature of thefuel is less than a predetermined value.
 10. The system of claim 1wherein the at least one sensor is a first at least one sensor and thesystem further comprises: a second at least one sensor positioned higherin the at least one tank by a predetermined space than the first atleast one sensor, the second at least one sensor being configured formeasuring the pressure of the fluid, the second at least one sensorbeing communicatively coupled to the at least one processor; and amemory coupled to the at least one processor, the memory includingcomputer program code executable by the at least one processor for:determining the density of the fluid with reference to the pressuremeasured by the first at least one sensor and the pressure measured bythe second at least one sensor; and determining at least one of thevolume, the quantity and the quality of fluid with reference to thepressure measured by the first at least one sensor and the determineddensity of the fluid in the tank.
 11. A system for determining volume offluid in at least one tank, the system comprising: at least one tankcapable of storing a volume of fluid; at least one differential pressuresensor positioned within the at least one tank, and submersed in fluidwhen fluid is in the at least one tank, the at least one differentialpressure sensor being configured for measuring pressure of fluidproximate to the position of the sensor in the at least one tank and foradjusting a measurement of fluid pressure by atmospheric pressure; andat least one processor in communication with the at least onedifferential pressure sensor and operable for generating fluid volumeoutput signals based on detected tank fluid pressure adjusted byatmospheric pressure.
 12. The system of claim 11, further comprising abuffer mesh positioned on the differential pressure sensor.
 13. Thesystem of claim 11 wherein the at least one sensor is also configuredfor measuring temperature of the fluid and generating a signalindicative of the temperature to ascertain whether a fuel frost orfreeze event could occur.
 14. The system of claim 11 further comprisinga memory coupled to the at least one processor, the memory includingcomputer program code executable by the at least one processor fordetermining the volume of fluid contained within the at least one tankand storing the determined volume data in memory.
 15. The system ofclaim 11 further comprising: a transmitter mounted on the vehicleconfigured for transmitting data signals to a remote server (RS); and amemory coupled to the at least one processor, the memory includingcomputer program code executable by the at least one processor forcausing the transmitter to transmit data signals indicative of thevolume of fluid as determined by the at least one processor.
 16. Thesystem of claim 11 wherein the at least one sensor also includes atemperature sensor and a heater communicatively coupled with the atleast one processor and is configured for measuring temperature of thefluid and activating the heater when the measured temperature of thefuel is less than a predetermined value.
 17. The system of claim 11further comprising a memory coupled to the at least one processor, thememory including computer program code executable by the at least oneprocessor for determining the volume of fluid contained within the atleast one tank and storing the determined volume data in memory.
 18. Thesystem of claim 11 further comprising: a transmitter configured fortransmitting data signals to a remote inventory management server (RS)and communicatively coupled to the at least one processor; and a memorycoupled to the at least one processor, the memory including computerprogram code executable by the at least one processor for: determiningthe volume of fluid with reference to the pressure and the density ofthe fluid; and causing the transmitter to transmit data signalsindicative of the volume of fluid to the RS, the RS including a secondprocessor and second memory coupled the second processor for executingcomputer program code for determining if fuel volume has changed morethan a predetermined threshold and for recording the volume subsequentto the change if it is determined that fuel volume has changed more thana predetermined threshold.
 19. The system of claim 11 wherein the atleast one sensor is a first at least one sensor and the system furthercomprises: a second at least one sensor positioned higher in the atleast one tank by a predetermined space than the first at least onesensor, the second at least one sensor being configured for measuringthe pressure of the fluid and communicating signals indicative of sameto the at least one processor; and a memory coupled to the at least oneprocessor, the memory including computer program code executable by theprocessor for determining the density of the fluid with reference to thepressure measured by the first at least one sensor and the pressuremeasured by the second at least one sensor.
 20. The system of claim 11further comprising a dry box attached the at least one vent line to aidin absorbing moisture and keeping air in the at least one vent line dry.21. The system of claim 11 further comprising a dry box coupled in fluidcommunication to the at least one sensor to aid in absorbing moistureand keeping air communicated to the at least one sensor dry.
 22. Asystem for determining volume of fluid in at least one tank, the systemcomprising: at least one tank mounted on a vehicle, the at least onetank being capable of storing a volume of fluid; at least onedifferential pressure sensor positioned within the at least one tank,and submersed in fluid when fluid is in the at least one tank, the atleast one sensor being configured for measuring pressure of fluidproximate the differential pressure sensor; at least one vent lineoperably connected to the at least one differential pressure sensor, theat least one vent line having a single end through which air may flowand atmospheric pressure may be communicated to the at least onedifferential pressure sensor, the at least one differential pressuresensor being further configured for adjusting a fluid pressure readingby the communicated atmospheric pressure; at least one processorpositioned within and coupled to the at least one differential pressuresensor; and a memory positioned within the at least one differentialpressure sensor and coupled to the at least one processor, the memoryincluding computer program code executable by the at least one processorfor performing at least two of the functions of determining volume offluid with reference to the pressure of fluid as adjusted by atmosphericpressure, determining the density of the fluid, storing data indicativeof the aforementioned determinations in memory, determining frompresently determined and previously stored data that fluid volume in thetank has changed by more than a predetermined threshold, and generatingan alert indication when it is determined that volume of fluid in thetank has changed by more than the predetermined threshold.
 23. Thesystem of claim 22, further comprising a buffer mesh positioned on thedifferential pressure sensor.
 24. The system of claim 22 wherein thesystem further comprises a transmitter in communication with andcontrolled by the at least one processor and configured for transmittingdata generated by the at least one processor to a remote server.
 25. Thesystem of claim 22 wherein the at least one sensor is a first at leastone sensor and the system further comprises a second at least one sensorpositioned higher in the at least one tank by a predetermined distancethan the first at least one sensor, the second at least one sensor beingconfigured for measuring the pressure of the fluid proximate the higherposition and communicating data indicative of the measured pressure tothe at least one processor.
 26. A system for determining volume of fluidin a fluid container, the system comprising: a fluid container capableof storing a volume of fluid; at least one differential pressure sensorpositioned within the fluid container, the differential pressure sensorbeing configured for measuring pressure of fluid surrounding thedifferential pressure sensor in the container; at least one vent lineoperably connected to the at least one differential pressure sensor, theat least one vent line having a single end through which air may flowand atmospheric pressure may be communicated to the at least onedifferential pressure sensor, the at least one differential pressuresensor being further configured for generating an output signalindicative of the differential pressure between the detected fluidpressure and the communicated atmospheric pressure; and at least oneprocessor constituting a part of the at least one differential pressuresensor and operable for determining the volume of fluid in the containeras a function of the generated output signal indicative of thedifferential pressures applied to the sensor.
 27. The system of claim 26additionally comprising: a transmitter configured for transmitting datato a remote server upon receiving instructions to do so from the atleast one processor; and memory, associated with the at least oneprocessor, the memory including computer program code executable by theprocessor for storing data indicative of the output signal generated bythe processor indicative of the differential pressures supplied to thesensor along with program code executable by the processor forperforming at least one of the functions of transmitting stored data tothe remote server and determining if fuel volume has changed more than apredetermined threshold whereby an alert is generated.
 28. The system ofclaim 26, further comprising a buffer mesh positioned on thedifferential pressure sensor.